Is hydropower renewable?

Hydropower – otherwise known as hydroelectricity – is a fast-growing form of energy generation. It has been used for more than 100 years, popularised in the USA with famous projects such as the Hoover Dam.

How do hydropower plants work?

Hydropower captures the kinetic energy of falling water and transforms it into mechanical energy. A dam stores water in a reservoir, then releases it in huge volumes to flow through a turbine. This spins and activates a generator, producing electricity.

Is hydropower renewable?

Hydropower has long been thought of by many as a ‘green’ energy generation, but it is not cut and dried one way or the other. Anything disrupting the natural balance of the ecosystem can be dangerous and the technology has a much larger carbon footprint than previously thought.

Water usage

It is argued that hydroelectricity is sustainable because its fuel, water, is constantly replenished. However, the massive volumes of water required are controversial considering the global water shortage due to climate change. This is, in fact, one of the main reasons people are calling for the closure of coal-fired power plants.

Impact on aquatic life

Hydroelectricity disrupts biological systems by changing the flow of rivers. It has an impact on fish and tides, blocking migrating fish from reaching their spawning grounds. Reservoirs also impact water temperatures and silt loads of rivers and streams.


Recent research has brought a new argument against the sustainability of hydropower: emissions.

When vegetation is trapped in reservoirs, it decomposes and stagnates the water, releasing greenhouse gases. Significant amounts of carbon dioxide and methane are generated, especially in warm environments. Methane is the real worry, as it is 34 times more potent than carbon dioxide and contributes to global warming, pollution and destruction of the ozone layer

There is no denying that reservoir emissions and biological disruption pose a threat to the planet, but there are pros and cons of all energy generation technologies; it is all about weighing these up. Hydropower plants are able to produce huge amounts of electricity without burning fossil fuels, but it comes at a cost. It can’t be considered fully ‘renewable’ by the accepted definition.